U.S. patent application number 12/130109 was filed with the patent office on 2008-12-04 for bonded plate for sink bowl and method of forming the sink bowl using the same through pressing.
This patent application is currently assigned to MATERIAL SCIENCES CORPORATION. Invention is credited to Bong-jun Lee, Hae-sik Lee.
Application Number | 20080299387 12/130109 |
Document ID | / |
Family ID | 40088601 |
Filed Date | 2008-12-04 |
United States Patent
Application |
20080299387 |
Kind Code |
A1 |
Lee; Hae-sik ; et
al. |
December 4, 2008 |
Bonded Plate for Sink Bowl and Method of Forming the Sink Bowl
Using the Same Through Pressing
Abstract
A bonded plate for a sink bowl, which has excellent
sound-absorbing, vibration-damping, and heat-insulating
characteristics, and a method of forming the sink bowl using the
same through pressing. The bonded plate includes a surface plate, a
backing plate backing the surface plate, and an adhesive resin
interposed between the surface plate and the backing plate and
bonding the surface plate and the backing plate with each other,
wherein the adhesive resin has a thickness from about 0.02 mm to
about 0.1 mm. Thereby, the adhesive resin layer of the bonded plate
can have sound-absorbing, vibration-damping, and
dew-condensation-preventing functions. Further, the sink bowl is
produced using the bonded plate, so that it can reduce the cost of
production, can provide formability equal to that of the
conventional sink bowl, and can produce excellent sound-absorbing,
vibration-damping, and dew-condensation-preventing effects.
Inventors: |
Lee; Hae-sik; (Gwangju,
KR) ; Lee; Bong-jun; (Gwangju, KR) |
Correspondence
Address: |
QUINN LAW GROUP, PLLC
39555 ORCHARD HILL PLACE, SUITE # 520
NOVI
MI
48375
US
|
Assignee: |
MATERIAL SCIENCES
CORPORATION
Elk Grove Village
IL
HAEWON MSC CO., LTD
Jeollanam-do
|
Family ID: |
40088601 |
Appl. No.: |
12/130109 |
Filed: |
May 30, 2008 |
Current U.S.
Class: |
428/339 ;
156/267 |
Current CPC
Class: |
B32B 1/00 20130101; B32B
2307/102 20130101; B32B 2309/105 20130101; B32B 15/20 20130101;
B32B 2307/714 20130101; B32B 2311/00 20130101; B32B 15/18 20130101;
B32B 7/12 20130101; Y10T 428/269 20150115; B32B 37/1207 20130101;
B32B 2307/304 20130101; Y10T 156/108 20150115; B32B 2307/56
20130101 |
Class at
Publication: |
428/339 ;
156/267 |
International
Class: |
B32B 17/10 20060101
B32B017/10; B32B 37/00 20060101 B32B037/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2007 |
KR |
10-2007-0053531 |
Claims
1. A bonded plate for a sink bowl, comprising: a surface plate; a
backing plate backing the surface plate; and an adhesive resin
interposed between the surface plate and the backing plate and
bonding the surface plate and the backing plate with each other,
wherein the adhesive resin has a thickness from about 0.02 mm to
about 0.1 mm, whereby improved excellent sound-absorbing,
vibration-damping and heat-insulating characteristics are
achievable from the bonded plate.
2. The bonded plate as set forth in claim 1, wherein the surface
plate has a thickness from about 0.1 mm to about 0.4 mm, and
wherein the backing plate has a thickness from about 0.4 mm to
about 1.2 mm.
3. The bonded plate as set forth in claim 2, wherein the surface
plate is formed of stainless steel, which has excellent corrosion
resistance and workability, and wherein the backing plate is formed
from one selected from the group consisting of a galvanized steel
sheet, a stainless steel sheet, an aluminum sheet, a polyester
painted steel sheet, a cold rolled steel sheet, and a pickled and
oiled steel sheet.
4. The bonded plate as set forth in claim 2, wherein each of the
surface plate and the backing plate has bending rigidity from about
10.5 Nm to about 16.5 Nm.
5. The bonded plate as set forth in claim 2, wherein the backing
plate further includes an anti-corrosion coating layer on a lower
surface thereof.
6. The bonded plate as set forth in claim 2, wherein the adhesive
resin has viscosity from about 2500 cps to about 4500 cps.
7. The bonded plate as set forth in claim 1, wherein the surface
plate is formed of stainless steel, which has excellent corrosion
resistance and workability, and wherein the backing plate is formed
from one selected from the group consisting of a galvanized steel
sheet, a stainless steel sheet, an aluminum sheet, a polyester
painted steel sheet, a cold rolled steel sheet, and a pickled and
oiled steel sheet.
8 . The bonded plate as set forth in claim 1, wherein each of the
surface plate and the backing plate has bending rigidity from about
10.5 Nm to about 16.5 Nm.
9. The bonded plate as set forth in claim 1, wherein the backing
plate further includes an anti-corrosion coating layer on a lower
surface thereof.
10. The bonded plate as set forth in claim 1, wherein the adhesive
resin has viscosity from about 2500 cps to about 4500 cps.
11. A method of forming a sink bowl using a bonded plate, the
method comprising the steps of: preparing the bonded plate bonding
a surface plate and a backing with an adhesive resin having
viscosity from 2500 cps to 4500 cps, so that the bonded plate has
excellent sound-absorbing, vibration-damping and heat-insulating
characteristics through multi-stage pressing; modeling the sink
bowl in a desired shape and sequentially pressing the bonded plate
using a first die capable of pressing the modeled sink bowl up to a
depth between 1/2 and 2/3 from the top of the sink bowl and a
second die capable of pressing the pressed sink bowl up to a bottom
of the modeled sink bowl; and cutting off surrounding unnecessary
portions of the pressed sink bowl using a trimming die.
12. The method as set forth in claim 11, wherein the bonded plate
includes the surface plate, the backing plate backing the surface
plate, and the adhesive resin interposed between the surface plate
and the backing plate and bonding the surface plate and the backing
plate with each other, wherein the adhesive resin has a thickness
from about 0.02 mm to about 0.1 mm, wherein the surface plate has a
thickness from about 0.1 mm to about 0.4 mm, and wherein the
backing plate has a thickness from about 0.4 mm to about 1.2
mm.
13. The method as set forth in claim 12, wherein the surface plate
is formed of stainless steel, which has excellent corrosion
resistance and workability, wherein the backing plate is formed
from any one selected from a galvanized steel sheet, a stainless
steel sheet, an aluminum sheet, a polyester painted steel sheet, a
cold rolled steel sheet, and a pickled and oiled steel sheet, and
wherein each of the surface plate and the backing plate has bending
rigidity from about 10.5 Nm to about 16.5 Nm.
14. The method as set forth in claim 11, wherein the surface plate
is formed of stainless steel, which has excellent corrosion
resistance and workability, wherein the backing plate is formed
from any one selected from a galvanized steel sheet, a stainless
steel sheet, an aluminum sheet, a polyester painted steel sheet, a
cold rolled steel sheet, and a pickled and oiled steel sheet, and
wherein each of the surface plate and the backing plate has bending
rigidity from about 10.5 Nm to about 16.5 Nm.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Republic of Korea Patent
Application 10-2007-0053531, filed on May 31, 2007.
TECHNICAL FIELD
[0002] The present invention relates to a bonded steel plate for a
sink bowl, which has excellent sound-absorbing, vibration-damping
and heat-insulating characteristics, and a method of press-forming
a sink bowl using the same bonded steel plate.
BACKGROUND OF THE INVENTION
[0003] In general, steel sheets themselves have very poor
sound-isolating, sound-absorbing, vibration-damping and
heat-insulating characteristics, and have limitations of wide
application to products, particularly, exposed to noise, vibration,
change in temperature, and so on. For this reason, conventionally,
the steel sheets make up for such characteristics by interposing a
sound absorbing material and a material having excellent
vibration-damping characteristics (e.g. vibration damping sheet,
paint, tape and the like) between two of them.
[0004] However, in the case of using the sound absorbing material,
etc. in this way, the sound absorbing material, etc. should be
separately installed when constructed, and particularly, in terms
of the workability, the sound absorbing material, etc. should be
separately worked so as to be compatible with the shape of each
steel sheet apart from steel sheet working.
[0005] Especially, in the case of producing a sink bowl using a
steel sheet (e.g. a stainless steel sheet), the sink bowl has an
advantage in that it is not cracked or fractured because the steel
sheet itself has high strength. However, the sink bowl has a
disadvantage in that, during washing-up, it collides with metal
tableware causing offensive noise as well as vibration propagating
along the same. Furthermore, the sink bowl causes dew condensation
by a temperature difference between inner and outer surfaces
thereof because the heat insulating characteristics of the steel
sheet are poor. Thus, conventionally, the dew condensation is
prevented by attaching a ball cover, which is capable of covering
the outer surface of the sink bowl to insulate heat. Further, in
order to block the noise and vibration, a method of attaching a
member such as an aluminum pad to the outer surface of the sink
bowl is employed. However, in the case of producing the entire sink
bowl using only the steel sheet (e.g. SUS 304), the sink bowl
increases the cost burden of the steel sheet. Further, the separate
subsidiary materials such as the ball cover and the aluminum pad
cause the sink bowl to incur additional cost. Furthermore, in terms
of the production process, a process of installing the subsidiary
materials is additionally required to increase the cost of
production.
SUMMARY OF THE INVENTION
[0006] Accordingly, the present invention provides a bonded steel
sheet, which can be applied to the products such as the sink bowl
requiring excellent sound-absorbing and vibration-damping
characteristics, removing the need to attach the separate
subsidiary materials due to its own sound-absorbing,
vibration-damping, and dew-condensation-preventing characteristics,
and be wrought in various shapes due to excellent workability (e.g.
pressing).
[0007] The present invention has been made keeping in mind the
above problems occurring in the prior art, and an object of the
present invention is to provide a bonded plate, which bonds a
surface plate with a backing plate using the adhesive resin,
thereby allowing a layer of the adhesive resin thereof to have
sound-absorbing, vibration-damping, and dew-condensation-preventing
functions, and which is used to produce a sink bowl, thereby
reducing the cost of production, providing formability equal to
that of a conventional sink bowl, and producing excellent
sound-absorbing, vibration-damping and dew-condensation-preventing
effects of the sink bowl.
[0008] Another object of the present invention is to provide a
bonded plate, which has an adhesive resin maintaining a
predetermined viscosity, thereby preventing an adhesive resin layer
itself from being fractured, and increasing sound-absorbing,
vibration-damping and heat-insulating characteristics due to such
viscosity.
[0009] Meanwhile, in order to solve the problem that the cost of
production is sharply increased in the case of using a conventional
single steel sheet made of relatively expensive stainless steel,
etc., an object of the present invention is to provide a bonded
plate, in which a surface plate exposed to the outside is formed
thin using a steel sheet having excellent corrosion resistance and
workability, and simultaneously a backing plate backing the surface
plate inside is formed of a relatively inexpensive steel sheet and
is bonded with the surface plate using an adhesive resin having
excellent sound-absorbing, vibration-damping, and heat-insulating
characteristics, thereby remarkably reducing the cost of
production.
[0010] According to an aspect of the present invention, there is
provided a bonded plate for a sink bowl, having excellent
sound-absorbing, vibration-damping, and heat-insulating
characteristics. The bonded plate includes: a surface plate; a
backing plate backing the surface plate; and an adhesive resin
interposed between the surface plate and the backing plate and
bonding the surface plate and the backing plate with each other,
wherein the adhesive resin has a thickness from about 0.02 mm to
about 0.1 mm.
[0011] Here, the surface plate may have a thickness from about 0.1
mm to about 0.4 mm, and the backing plate may have a thickness from
about 0.4 mm to about 1.2 mm.
[0012] Further, the surface plate may be formed of stainless steel,
which has excellent corrosion resistance and workability, and the
backing plate may be formed from any one selected from a galvanized
steel sheet, a stainless steel sheet, an aluminum sheet, a
polyester painted steel sheet, a cold rolled steel sheet, and a
pickled and oiled steel sheet.
[0013] Also, the surface plate and the backing plate may each have
bending rigidity from about 10.5 Nm to about 16.5 Nm.
[0014] Meanwhile, the backing plate may further include an
anti-corrosion coating layer on a lower surface thereof.
[0015] Further, the adhesive resin may have viscosity from about
2500 cps to about 4500 cps.
[0016] According to another aspect of the present invention, there
is provided a method of forming a sink bowl using a bonded plate
having excellent sound-absorbing, vibration-damping, and
heat-insulating characteristics through multi-stage pressing. The
method includes the steps of: preparing the bonded plate by bonding
a surface plate and a backing plate with an adhesive resin having
viscosity from 2500 cps to 4500 cps; modeling the sink bowl in a
desired shape by sequentially pressing the bonded plate using a
first die capable of pressing the modeled sink bowl up to a depth
between 1/2 and 2/3 from the top of the sink bowl and a second die
capable of pressing the pressed sink bowl up to a bottom of the
modeled sink bowl; and cutting off surrounding unnecessary portions
of the pressed sink bowl using a trimming die.
[0017] Here, the bonded plate may include the surface plate, the
backing plate backing the surface plate, and the adhesive resin
interposed between the surface plate and the backing plate and
bonding the surface plate and the backing plate with each other;
the adhesive resin may have a thickness from about 0.02 mm to about
0.1 mm; the surface plate may have a thickness from about 0.1 mm to
about 0.4 mm; and the backing plate may have a thickness from about
0.4 mm to about 1.2 mm.
[0018] Further, the surface plate may be formed of stainless steel,
which has excellent corrosion resistance and workability; the
backing plate may be formed from any one selected from a galvanized
steel sheet, a stainless steel sheet, an aluminum sheet, a
polyester painted steel sheet, a cold rolled steel sheet, and a
pickled and oiled steel sheet; and the surface plate and the
backing plate may each have bending rigidity from about 10.5 Nm to
about 16.5 Nm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other objects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description when taken in conjunction with the
accompanying drawings, in which:
[0020] FIG. 1 is a partial perspective view illustrating the
structure of a bonded plate according to an embodiment of the
present invention;
[0021] FIG. 2 is a sectional view taken along the line A-A of FIG.
1;
[0022] FIG. 3 is a perspective view illustrating a sink bowl
produced using a bonded plate according to the present invention;
and
[0023] FIG. 4 is a conceptual view taken illustrating a method of
forming a sink bowl using a bonded plate through pressing according
to another embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Hereinafter, a bonded plate and a sink bowl using the same,
according to the present invention, will be described in greater
detail with reference to the accompanying drawings.
Structure of Bonded Plate
[0025] FIG. 1 is a partial perspective view illustrating the
structure of a bonded plate according to an embodiment of the
present invention, and FIG. 2 is a sectional view taken along the
line A-A of FIG. 1.
[0026] As illustrated in FIGS. 1 and 2, the bonded plate 10
according to the present invention includes a surface plate 11, a
backing plate 12 backing the surface plate 11, and an adhesive
resin 13 interposed between the surface plate 11 and the backing
plate 12 to bond the surface and backing plates 11 and 12 with each
other.
[0027] Preferably, the surface plate 11 is made of stainless steel,
which has excellent workability and corrosion resistance, and the
backing plate 12 is selected from a galvanized steel sheet, a
stainless steel sheet, an aluminum sheet, a polyester painted steel
sheet, a cold rolled steel sheet, or a pickled and oiled steel
sheet. More preferably, the surface plate 11 employs any one of the
SUS 300 series having excellent workability and corrosion
resistance (and most preferably SUS 304). The surface plate 11 is
essential to have the corrosion resistance for preventing rust from
being generated, because the sink bowl by nature is always exposed
to moisture and chemical components (e.g. a detergent). Further, it
is apparent that the bonded plate 10 should make use of a material
having excellent formability, because the sink bowl should be
formed using the bonded plate 10 according to the present
invention.
[0028] Meanwhile, the backing plate 12 is preferably selected from
the steel sheets, which have excellent workability in order to
secure the formability of the entire bonded plate 11 so as to bend
the bonded plate 10 as well as enough strength to back the surface
plate 11. Specifically, the backing plate 12 can employ a
galvanized steel sheet, a stainless steel sheet, an aluminum sheet,
a polyester painted steel sheet, a cold rolled steel sheet, or a
pickled and oiled steel sheet. Here, the galvanized steel sheet
should be broadly interpreted to include a hot dip galvanized steel
sheet, an electrolytic galvanized steel sheet, a galvannealed steel
sheet, an aluminum coated steel sheet, a zinc-aluminum alloy coated
steel sheet and so on.
[0029] As described above, the surface plate 11 and the backing
plate 12 should have excellent formability in order to form the
bonded plate 10 into products having various shapes. In order to
meet this formability, the bonded plate is preferably selected from
materials having bending rigidity from 10.5 Nm to 16.5 Nm.
[0030] The bending rigidity is calculated using a Ross Kerwin Ungar
(RKU) method expressed by Equation 1 below:
E = 12 ( 1 - .upsilon. 2 ) B c t c 3 , Equation 1 ##EQU00001##
where B.sub.c is the bending rigidity, .upsilon. is the Poisson's
ratio, and t.sub.c is the total thickness.
[0031] Particularly, when the bending rigidity is less than 10.5
Nm, the bonded plate 10 is warped by weak force, and thus can be
vulnerable to external impact after formation. In contrast, when
the bending rigidity is more than 16.5 Nm, the bonded plate 10 has
reduced formability, and thus cannot be smoothly formed into the
products such as the sink bowl.
[0032] The adhesive resin 13 is interposed between the surface
plate 11 and the backing plate 12, and functions to bond the
surface and backing plate 11 and 12 with each other. Preferably,
the adhesive resin 13 is formed at a thickness from 0.02 mm to 0.1
mm. Because the adhesive resin 13 is interposed between the surface
and backing plates 11 and 12 to serve as a shock-absorbing and
heat-insulating material, it enables the entire bonded plate 10 to
produce excellent sound-absorbing, heat-insulating, and
vibration-damping effects. In other words, a layer of the adhesive
resin 13 functions to bond the surface plate 11 and the backing
plate 12, and simultaneously damp the vibration and noise applied
from the outside. Furthermore, the adhesive resin layer serves as
the heat-insulating material, and thus inhibits dew condensation
from being generated from the sink bowl.
[0033] Preferably, the adhesive resin used in the present invention
has viscosity from 2500 cps to 4500 cps. When the viscosity is less
than 2500 cps, the viscosity of the adhesive resin is too low, so
that the adhesive resin cannot firmly bond the surface plate and
the backing plate. In contrast, when the viscosity is more than
4500 cps, the viscosity of the adhesive resin is too high, so that,
in the case of forming and working the bonded plate, part of the
cured adhesive resin layer is fractured, or the surface plate of
the bonded plate is warped. Thus, the adhesive resin used for the
bonded plate of the present invention should maintain the viscosity
of a predetermined level in order to guarantee excellent
formability. Further, due to such viscosity, the adhesive resin can
further increase vibration-damping, sound-absorbing,
heat-insulating effects.
[0034] Preferably, the surface plate is formed to have a thickness
from 0.1 mm to 0.4 mm, the backing plate 12 is formed to have a
thickness from 0.4 mm to 1.2 mm, and the adhesive resin 13 bonding
the surface plate 11 with the backing plate 12 is formed to have a
thickness from 0.02 mm to 0.1 mm. In order to solve the problem
that the cost of production sharply increases in the case of using
the conventional single steel sheet made of relatively expensive
stainless steel, etc., the present invention is technically
characterized in that the surface plate 11, which requires
excellent corrosion resistance and workability due to the exposure
to the outside, is formed thin, and simultaneously the backing
plate 12 backing the surface plate inside is thickly formed of the
relatively inexpensive steel sheet, and is bonded with the surface
plate 11 using the adhesive resin 13 having excellent sound and
vibration damping characteristics. Preferably, the surface plate 11
is formed to have a thickness from 0.1 mm to 0.4 mm. When the
surface plate 11 has a thickness of 0.1 mm or less, it is too thin,
and thus itself is warped or torn by impact applied from the
outside. In contrast, when the surface plate 11 has a thickness of
0.4 mm or more, the effect of reducing the cost of production is
relatively lowered. Meanwhile, the adhesive resin 13 is formed to
have a thickness from 0.02 mm to 0.1 mm. When the adhesive resin 13
has a thickness of 0.02 mm or less, the sound-absorbing,
vibration-damping, and heat-insulating characteristics are lowered.
In contrast, when the adhesive resin 13 has a thickness of 0.1 mm
or more, the adhesive resin layer cannot maintain uniform viscosity
in the thickness direction.
[0035] More preferably, the backing plate 12 may be provided with
an anti-corrosion coating layer on a lower surface thereof. This is
because the backing plate 12 uses the relatively inexpensive
ordinary steel sheet unlike the surface plate, and thus has a
possibility of generating internal corrosion when used for a long
time.
Method of Forming Sink Bowl Using Bonded Plate through Multi-stage
Pressing
[0036] FIG. 3 is a perspective view illustrating a sink bowl 20
produced using a bonded plate according to the present invention,
and FIG. 4 is a conceptual view taken illustrating a method of
forming a sink bowl using a bonded plate through pressing according
to another embodiment of the present invention.
[0037] The method of forming the sink bowl 20 of FIG. 3 using the
above-described bonded plate with reference to FIG. 4 will be
described below.
[0038] The method of forming a sink bowl 20 using a bonded plate 10
according to another embodiment of the present invention includes
preparing the bonded plate 10 by bonding a surface plate 11 and a
backing with an adhesive resin 13 having viscosity from 2500 cps to
4500 cps; modeling the sink bowl in a desired shape and
sequentially pressing the bonded plate 10 using a first die 32
capable of pressing the modeled sink bowl up to a depth between 1/2
and 2/3 from the top of the sink bowl and a second die 34 capable
of pressing the pressed sink bowl up to the bottom of the modeled
sink bowl; and cutting off or trimming surrounding unnecessary
portions of the pressed sink bowl using a trimming die 36.
[0039] As described above, the reason of continuously pressing the
sink bowl 20 using the first and second dies 32 and 34 is because
the bonded plate is torn when pressed once. For this reason, the
sink bowl 20 is formed in a desired shape by multi-stage pressing,
for instance, two-stage pressing.
[0040] In particular, because the bonded plate 10 is made by
bonding homogeneous and heterogeneous steel sheets using the
adhesive resin 13, the steel sheets of the bonded plate 10 can be
mutually pushed and separated relative to each other by force
applied in one direction when pressed. Thus, the homogeneous and
heterogeneous steel sheets are bonded with each other using the
adhesive resin 13 having a predetermined viscosity, so that they
can have excellent shear resistance to minimize the separation.
Furthermore, the adhesive resin 13 used for the present invention
has the viscosity from 2500 cps to 4500 cps, so that, although the
steel sheets of the bonded plate 10 are pushed against each other,
it can still maintain adhesive force in the pushed state. Further,
in the trimming process, the unnecessary portion of the edge of the
bonded plate is cut off. Finally, the bottom and sidewall of the
sink bowl 20 are provided with a drainage hole for draining the
water and an overflow hole for preventing the sink bowl from
overflowing. Thereby, a final product is produced.
[0041] As is apparent from the above description, the present
invention has the following effects. First, the bonded plate 10,
which has the surface plate 11 bonded with the backing plate 12
using the adhesive resin 13, is used, so that the adhesive resin
layer of the bonded plate 10 can have sound-absorbing,
vibration-damping and dew-condensation-preventing functions.
Further, the sink bowl 20 is produced using the bonded plate 10, so
that it can remarkably reduce the cost of production, can secure
formability equal to that of the conventional sink bowl, and can
produce excellent sound-absorbing, vibration-damping, and
dew-condensation-preventing effects.
[0042] Second, the bonded plate 10 maintains the adhesive resin 13
thereof to have a predetermined viscosity, so that, when the bonded
plate 10 is formed, the adhesive resin layer itself is not
fractured, and can increase sound-absorbing, vibration-damping, and
heat-insulating characteristics due to such viscosity.
[0043] Third, in order to solve the problem that the cost of
production sharply increases in the case of using the conventional
single steel sheet made of relatively expensive stainless steel,
etc., the bonded plate 10 is produced in such a manner that the
surface plate 11 exposed to the outside is formed thin using the
steel sheet having excellent corrosion resistance and workability,
and simultaneously the backing plate 12 backing the surface plate
11 inside is formed from the relatively inexpensive steel sheet and
is bonded with the surface plate 11 using the adhesive resin 13
having excellent sound-absorbing, vibration-damping and
heat-insulating characteristics, so that it can remarkably reduce
the cost of production.
[0044] Although the exemplary embodiments of the present invention
have been described for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as defined in the accompanying claims.
* * * * *